A WEEK of monsoon misery is underway as thunderstorms triggered by the heatwave erupt all over Britain.

But though it will feel slightly cooler, temperatures will stay above average for the time of year right into August, say ­forecasters.

A level-three health alert remains in place this morning with the heat posing a risk to elderly and vulnerable people.

The Met Office has issued a severe weather warning for heavy rain today, after swathes of the country were lashed by storms yesterday.

More than two inches of rain fell in Pershore, Worcestershire, in 12 hours.

Ferocious electrical storms have seen around 50,000 lightning strikes this week.

In Heanor, Derbyshire, a ­massive lightning bolt sparked a fire after hitting the roof of a family home yesterday.

Three adults and a child were inside at the time and they and neighbours were forced to flee into the street.

In Manchester, rail signals were damaged by a lightning strike with some journeys delayed by up to 90 minutes.

A house in Heanor, Derbyshire caught fire after being struck by lightning

Other parts of the country were hit by floods with travel services in the North, West ­Midlands, East Anglia, ­Birmingham and southern England all affected.

Met Office forecaster Sarah Holland said: “It is a very unsettled picture for the next few days with more rain coming through Wednesday and Thursday. It is also going to stay very warm and humid with showers around at the weekend.”

The wet and wild picture comes as Britain swelters in the longest heatwave since the historic sizzler of 1976.

Temperatures have rocketed to 82F (28C) every day for almost three weeks, peaking at 92.3F on Tuesday at Heathrow.

It is a very unsettled picture for the next few days with more rain coming through Wednesday and Thursday

Met Office's Sarah Holland

The Met Office’s chief forecaster Nick Grahame said: “Air laden with moisture has arrived in the UK from France and the Altantic. As it is hot, it rises and rises in the atmosphere until it just goes bang, and that is what we are seeing.”

Jonathan Powell, forecaster for Vantage Weather Services, said: “These storms are going to rattle on through this week and into the weekend.

“It is also going to stay hot and very muggy really into the beginning of August and these are perfect conditions for more thunder.”

Lifeguards pulled 13 body boarders and two swimmers to safety yesterday after they were caught out by strong currents at Perranporth, Cornwall.